Pain measurement has generally been substantially subjective. That is, while diagnostic procedures (e.g., MRI, x-ray, ultrasound, etc.) provide data allowing for accurate determinations of the physiological condition, pain is almost always measured by asking for feedback from the patient. For example, in situations where opioids and/or other analgesics are being administered, and particularly, in Patient Controlled Analgesia (PCA), it would be desirable to measure objectively the pain experienced by the patient to surveil, and possibly over-ride, unwarranted and excessive administration of analgesia. Undertreatment of acute and especially chronic pain is widespread and often occurs because physicians have no objective way to assess patients' pain reports, especially in cases where the source of pain is not identifiable on routine anatomically based radiological studies or routine diagnostic electrophysiological studies of the peripheral nervous system. Even in emergency departments, when evaluating or treating a patient with a broken leg or dislocated shoulder, the staff may undertreat or overtreat with analgesia, selecting the level based on little more than past experience on the assumption that all patients respond similarly to similar dosages.
The lack of such objective assessment also impairs the control of Patient Controlled Analgesia (PCA)—narcotics delivered intravenously via a pump controlling both a basal rate of the dose infused hourly as well as a dose and frequency of additional narcotic a patient may self administer per hour. If a patient is in pain despite the basal and additional bolus narcotic administration, the pump parameters must be adjusted upward. This process which requires the attention of trained nursing staff and the orders of a physician may cause unfortunate delay and unnecessary pain before the PCA parameters are properly adjusted. Furthermore, relying heavily on patient reports of pain provides opportunities for patients to manipulate the physician to obtain more pain medication than is necessary.
As animals are unable to provide subjective assessments of their pain levels and the extent of discomfort can only be guessed at by noting behavioral changes (e.g., limping), an objective measurement of pain would be particularly valuable.
In addition to medical applications, quantitative reference data may be important in any situation where it may be necessary to objectively assess a level of pain (e.g., lawsuits, insurance and disability claims, etc.).
Brain imaging methods such as Positron Emission Tomography (PET), Single Photon Emission Computed Tomography (SPECT) and Functional Magnetic Resonance Imaging (fMRI) are sometimes used to help understand pain processing mechanisms in those with acute, experimentally created, and less commonly, chronic pain. Low resolution qEEG brain imaging methods such as LORETA (Pascual-Marqui et al 1999) may be used to provide physiological information about the brain regions involved in processing various types of acute and/or chronic pain, as well as the effect of treatment on the physiological activity of these regions but have provided no objective measures of pain.